Making Programming Easier
by Making it More Natural
Brad A. Myers
Human-Computer Interaction Institute
School of Computer Science
Carnegie Mellon University
http://www.cs.cmu.edu/~bam
bam@cs.cmu.edu
1
The User Interface of Programming Languages
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Programming is a human activity
Want to improve the ability of people to program
It makes sense to look at the human side
Brad Myers
CMU - HCI Institute
2
Who are the Authors?
• Not just professional programmers
– Many languages aimed at
“part-time” or novice programmers
• End User Programming!
Brad Myers
CMU - HCI Institute
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Why EUP?
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By 2005, 55 million end-user programmers
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Compared to only 2.75 million professional programmers
Use spreadsheets, CAD systems, special-purpose
scripting and visual languages, etc.
These languages are unnecessarily hard to use
and prone to errors

Errors in spreadsheets and other end-user-created
software costs companies millions of dollars
Brad Myers
CMU - HCI Institute
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Design of New Languages

How make design decisions?
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Designer’s intuition
Similarity to other languages
 But many have known problems
Key concept:

If you care about usability and learnability:
Can leverage off of what is known and
what can be learned about people
to guide design decisions
Brad Myers
CMU - HCI Institute
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“Millions for compilers but hardly a penny for understanding
human programming language use. Now, programming
languages are obviously symmetrical, the computer on one
side, the programmer on the other. In an appropriate
science of computer languages, one would expect that half
the effort would be on the computer side, understanding
how to translate the languages into executable form, and
half on the human side, understanding how to design
languages that are easy or productive to use.... The human
and computer parts of programming languages have
developed in radical asymmetry.”
— Allen Newell and Stuart Card, 1985
Brad Myers
CMU - HCI Institute
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Examples of Problems
The men and women here raise your hands!
if is_man(x) and is_woman(x) then raise_hand(x);

This issue with “and” applies to other natural
languages as well.
Find a paint that is not red or orange
not (paint.color == red) or paint.color == orange
not

(paint.color
== red or paint.color == orange
)
Research shows that these differences between
natural languages and computer languages hurt
understanding
Brad Myers
CMU - HCI Institute
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Why Study This?
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There are many known problems
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Little knowledge to guide designs
The language which is currently popular seems to
have about a 7 year window
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Fortran, PL/1, Pascal, C, C++, Java, (maybe C# ?) …
So new languages are always being created
We may influence design by identifying problems
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Programming is still hard to learn and hard to do
Java / C# took some into account
We certainly won't if we don't try, or if we don't
know what to say!
Brad Myers
CMU - HCI Institute
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Gentle Slope Systems
Programming in C++
Visual Basic
LabView
MFC
C Programming
Difficulty
of
Use
C Programming
Basic
Program Complexity and Sophistication
Goal
What we are doing...
Studying the People
Natural Programming Research

Try to provide a more scientific basis for
programming language design
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Apply results of Empirical Studies of Programmers
and Human-Computer Interaction to programming
language design
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New studies to fill in gaps

Design new programming languages and
environments based on these results
Brad Myers
CMU - HCI Institute
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Why Would Being Natural be Good?

Language should be close to user’s plan

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“Programming is the process of transforming a mental
plan into one that is compatible with the computer.”
— Jean-Michel Hoc
Example:

Inserting item into 3rd place of high score list
 Easy by Direct Manipulation (in a spreadsheet)
 Difficult to program:
 Loop, starting at end of array, shuffle items down,
then insert
Brad Myers
CMU - HCI Institute
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Why Would Being Natural be Good? #2

Directness (as in “Direct Manipulation”)
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“Distance between one's goals and the actions required
by the system to achieve those goals.”
— Hutchins, Hollan and Norman

Example:
vs.
Let Shape1.FillColor = &H00FF00FF&
Brad Myers
CMU - HCI Institute
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Background Research

Empirical Studies of Programmers and HCI results
not being used in the design of new languages
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30 years of research on what makes languages hard to
learn and error-prone
Java / C# looping, etc.
Summarized in our comprehensive tech report
—
John Pane and Brad Myers, “Usability Issues in the Design of
Novice Programming Systems” TR# CMU-CS-96-132. Aug, 1996.
http://www.cs.cmu.edu/~pane/cmu-cs-96-132.html
Brad Myers
CMU - HCI Institute
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Our Research
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Lots of gaps in prior research on people and
programming
Develop knowledge that can be used in design
Ph.D. thesis of John Pane
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Available at:
http://www-2.cs.cmu.edu/~pane/thesis/
Brad Myers
CMU - HCI Institute
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Natural Programming Studies

How people naturally express programming concepts
and algorithms
1) Nine scenes from PacMan
2) Transforming and calculating data in a spreadsheet
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Specific issues of language design
3) Selecting specific objects from a group (“and”, “or”, “not”)
Brad Myers
CMU - HCI Institute
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Experimental Design
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Question should not bias the answer
So use pictures instead of textual descriptions
Concentrate on kids, non-programmers
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Subjects should not be “tainted” by programming
knowledge
But test that the results generalize to adults and
programmers
Brad Myers
CMU - HCI Institute
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Study 1
Usually Pacman moves like this.
Now let's say we add a wall.
Pacman moves like this.
Not like this.
Do this: Write a statement that summarizes
how I (as the computer) should move Pacman
in relation to the presence or absence of other
things.
Second Study

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Whether similar results from other domains and
with adults
Developed 11 questions with scenarios using
spreadsheets
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To test database access and operations
More conventionally “computational”
Brad Myers
CMU - HCI Institute
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Example Question, 2nd Study
Question 4
• Describe in detailed steps what the computer should do to
categorize these people into 2 groups of ‘Gold’ and ‘Black’.
First
name
1 Sandra
2 Bill
3 Cindy
4 Tom
5 Bill
6 Whitney
7 Michael
8 Jay
9 David
10 Will
No.
Last
name
Bullock
Clinton
Crawford
Cruise
Gates
Houston
Jordan
Leno
Letterman
Smith
Group
Brad Myers
CMU - HCI Institute
First
name
1 Sandra
2 Bill
3 Cindy
4 Tom
5 Bill
6 Whitney
7 Michael
8 Jay
9 David
10 Will
No.
Last
name
Bullock
Clinton
Crawford
Cruise
Gates
Houston
Jordan
Leno
Letterman
Smith
Group
Gold
Gold
Gold
Gold
Black
Gold
Gold
Black
Black
Gold
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Results
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Rule-based style
“If PacMan loses all his lives, its game over.”
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Some use of Constraint style:
“Pacman cannot go through a wall.”
Set operations instead of iterations
“Subtract 20,000 from all elements in Round 2”
— These tend to eliminate control structures
Brad Myers
CMU - HCI Institute
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More Results
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Most arithmetic used natural language style
“When PacMan eats a big dot, the score goes up 100.”
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Operations suggest data as lists, not arrays
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Objects normally moving
“If PacMan hits a wall, he stops.”
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People don’t make space before inserting
so objects remember their own state
2/3 of the first study subjects drew pictures
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Usually to define the initial state
Brad Myers
CMU - HCI Institute
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Implications for New Languages
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Use event-based style for dynamic events
Provide operations on groups of objects
Work to minimize the need for control structures
and variables
Data structures that combine the capabilities of
lists + arrays + sets
Support simple arithmetic in natural language
style (“add 1 to score”)
Using mathematical notation such as > <  
rather than words achieves better accuracy
Brad Myers
CMU - HCI Institute
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New Language and System: HANDS
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Video
Brad Myers
CMU - HCI Institute
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Conclusions
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Can evaluate languages as to extent they
are “natural”
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Can use this technique to answer questions for language
designs
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Based on consistency, learnability, etc.
Instead of just using the designer’s intuition
Hopefully our data can help
Languages can be evaluated just like any other user
interface using HCI principles and techniques
If you want a useable and learnable programming language,
there are data and techniques that can help
Brad Myers
CMU - HCI Institute
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Credits
Support for this research has come in part from the
National Science Foundation under
Grant No. IRI-9900452
and
Grant No. IIS-9817527
For more information, see:
http://www.cs.cmu.edu/~NatProg
Brad Myers
CMU - HCI Institute
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Talk Given Using


Slide Show Commander
Developed as part of the
Pebbles Project
http://www.cs.cmu.edu/~pebbles

Available commercially
http://www.slideshowcommander.com/
Making Programming Easier
by Making it More Natural
Brad A. Myers
Human-Computer Interaction Institute
School of Computer Science
Carnegie Mellon University
http://www.cs.cmu.edu/~bam
bam@cs.cmu.edu
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